The present invention relates to a glass paste having photosensitivity, and more specifically to a photosensitive glass paste employed for forming barriers (also referred to as ribs or barrier ribs) for use in a plasma display panel (PDP).
Conventionally, barriers for a PDP were formed initially by a screen printing method. According to this method, however, printing is required to be repeatedly carried out, which involves difficult alignment operations and makes the whole process complicated, and further the resolution obtained is limited, which makes it difficult to form a high definition panel by the screen printing method. Therefore, recently, a sand blasting method has become a mainstream method employed in making barriers for the PDP.
However, although the sand blasting method is excellent in the accuracy of machining, it has other drawbacks: the process is complicated and time-consuming, the use of abrasive materials makes it difficult to perform contamination control, and it is difficult to form a high definition panel by the sand blasting method. Under these circumstances, a photosensitive paste method has come to attention in the art.
The photosensitive paste method is carried out by an apparently very simple process. That is, a substrate is coated with a photosensitive glass paste prepared by mixing a photosensitive resin material and an inorganic material containing glass having a low melting point. Then, patterning of barriers is carried out by a photolithographic process. Finally, firing of the patterned barriers is carried out. The photosensitive paste method, however, suffers from the problem that since the paste is a mixture of a resin material for imparting photosensitivity thereto and an inorganic material including a glass having a low melting point, scattering of light occurs at an interface between these materials, which produces unnecessarily exposed portions of the photosensitive glass paste.
To solve this problem, there have been proposed a method of mixing the photosensitive glass paste with a black pigment (Japanese Provisional Patent Publication (Kokai) No. 6-144871) and a method of mixing the paste with an ultraviolet absorber and at the same time using a resin having a high photosensitivity and a high resolution (Japanese Provisional Patent Publication (Kokai) No. 8-50811).
The former, however, has the inconvenience that the optical transmittance of the resulting glass paste is markedly reduced and light cannot reach a desired depth, so that it is required to repeatedly carry out the process of alignment.fwdarw.coating.fwdarw.exposure.fwdarw.development, which extremely degrades manufacturing efficiency or productivity. Although, the latter provides some improvement in the manufacturing efficiency, it suffers from another problem that its resin per se is adversely affected by oxygen during the exposure of the glass paste to ultraviolet rays.